1. Field of the Invention
The invention generally relates to a method and apparatus for making a multiple layer optical discs, and more particularly relates to a method and apparatus for separating the base plate from a mold plate when fabricating an optical disc.
2. Related Art
Optical discs have recently become the most popular storage media for data or information. Recordable discs and pressed discs are two kinds of optical discs that can carry data. A recordable (or rewritable) disc is made first with a base plate of carbon fiber. A layer of organic dye is then applied on the base plate for forming a data-recordable layer that is formed by a photochemical reaction. A beam-reflection layer and a protection layer are further applied on the disc to create a finished product ready for recording. The pressed discs are applied for mass production of data-ready discs. The original data are transformed into a laser signal beam for forming a master through opto-machining and plating processes. A stamp is made from the master for fabricating disc products. A recording layer and an adhesive layer are applied on the stamp, which are pressed and adhered to a base plate. Then, the base plate with recording layer carrying data patterns is separated from the stamp. Finally, a protection layer is applied on the data surface to finish the optical disc.
Prior methods for separating the base plate 10 from the mold plate 30 are based on different diameters of the two. As shown in FIG. 1, the outer diameter of the base plate 10 can be larger than that of the mold plate 30 so that the force from the forcing member 60 can be applied at the outer rim of the base plate 10. In this manner, excessive adhesive gathers on the rim of the base plate 10, as shown in FIG. 3, which makes separation difficult. The excessive adhesive also makes the recording layer uneven and loose from the base plate 10, which causes false reading of data. If, as shown in FIG. 2, the inner diameter of the base plate 10 is smaller than that of the mold plate 30, no excessive adhesive gathers on the rim, but the separating force from the forcing member 60 applied on the center of the base plate 10 easily deforms the base plate 10 and makes the disc unusable. Table 1 lists deformation characteristics of optical discs made with the inner pressing method of prior arts.
Therefore, a new method is needed that will solve the aforesaid problems of excessive adhesive and deformation when separating the base plate from the mold plate.